Statutory requirements - Summary of statutory information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)
Bermuda | SiriusPoint Bermuda
Statutory Accounting Practices [Line Items]
Statutory net income (loss)	$ 149.1
Bermuda | Alstead Re
Statutory Accounting Practices [Line Items]
Statutory net income (loss)	(0.4)
U.S. | SiriusPoint America
Statutory Accounting Practices [Line Items]
Actual statutory capital and surplus	581.5
Required statutory capital and surplus	112.4
Statutory net income (loss)	28.9
U.S. | Sirius Specialty
Statutory Accounting Practices [Line Items]
Actual statutory capital and surplus	55.2
Required statutory capital and surplus	47.0
Statutory net income (loss)	(7.1)
U.S. | Oakwood
Statutory Accounting Practices [Line Items]
Actual statutory capital and surplus	39.7
Required statutory capital and surplus	7.5
Statutory net income (loss)	$ (0.4)